Interesting question, I'd like to know to. One additional question : Does that accuracy stay when you're indoors? And do you even have a GPS signal indoors?Because my GPS for my car doesn't receive anything indoors...

Logged

To relax after some hard work on robotics: A very fun free online text based MMORPGorgcrime.net

A buddy of mine works at a place that makes GPS "analyzers"... they analyze the amount of potential error based on your location and altitude. For example, where I sit, a GPS reading may be +/- 1 meter in accuracy... where you sit, the same GPS may only be +/- 5 meters in accuracy. It all depends on where you are as to how accurate of a reading you get.

So as Steve Joblin was hinting at, you got really lucky on your accuracy. But still, this is a better accuracy than I was led to believe . . .

Anyway, the expert was telling us that WAAS and DGPS technology will be greatly improved in the next decade or so. He also said there was new technology being worked on that factors in the atmosphere conditions too (which affects speed of light/GPS transmissions).

So using a GPS for navigation on a small indoor robot would not work very well then I guess. 1-5 meter would be the make you wonder if its even in the right room

Will the offset be constant? Say if you do a reading an the GPS tells you that where you are, but in reality you are 1.3 meters longer to the right. If you move and do a new reading, will you still be 1.3 meters from the new position? Or does it change all the time?

From what I've been studying it the average position changes slowly over time...So a reading you took yesterday at one spot might be 5m off the next day.It seems like there are two kinds of problems you have to deal with:

1. Day to day drift, which can be fixed with an new offset from a known position on power up.

2. Noise coming in (this is the biggest part of the error) so that even if you are sitting still your GPS signal might tell you you are moving around a bit.

I've been studying (among other things ) way of improving gps and combining it with IMU/Odometry,and it seems workable but heavy on the maths (for me), but where is the fun if there is no challenge right?

Will the offset be constant? Say if you do a reading an the GPS tells you that where you are, but in reality you are 1.3 meters longer to the right. If you move and do a new reading, will you still be 1.3 meters from the new position? Or does it change all the time?

Quote

From what I've been studying it the average position changes slowly over time...So a reading you took yesterday at one spot might be 5m off the next day.

The satellites are always moving, and your gps would get a lock on different satellites at different periods of time. Atmosphere affects readings, which also changes. Nothing to keep the error constant . . .

Quote

So using a GPS for navigation on a small indoor robot would not work very well then I guess. 1-5 meter would be the make you wonder if its even in the right room

yeap. GPS also has a slow update frequency. the cheap ones update once every second or two - your robot wont know its run into something till its too late . . . which brings me to jesse's point:

Quote

I've been studying (among other things ) way of improving gps and combining it with IMU/Odometry,and it seems workable but heavy on the maths (for me), but where is the fun if there is no challenge right?

just so you know, that expert said this is the future of gps. gps and IMU's compliment each other well, it only requires kalman filters to make it happen . . . still too much math for me to fully understand, tho . . .